Frederick Law Olmsted is best remembered as the creator of such green space masterworks as New York’s Central Park, the grounds of the 1893 World’s Fair in Chicago and Stanford University’s campus.

But he was a restless, spirited man who engaged in a variety of endeavors. One of those — on the eve of the Civil War — involved Lawrence and the Bleeding Kansas struggles.

During the early 1850s, Olmsted made a name for himself as a journalist. He worked for a startup newspaper: The New York Daily Times (it would later drop the “Daily”). And he had an incredible assignment: Travel across the South, treating the region as a foreign correspondent would. Olmsted’s dispatches — penetrating, balanced, humane — were eagerly read by Northerners looking for a window into the Southern mindset and intentions. Along the way, given all that he witnessed, Olmsted became a fervent abolitionist.

In 1855, a man named James Abbott arranged a meeting with Olmsted. Abbott was one of the many people who had moved to Kansas under the aegis of the New England Emigrant Aid Co. This was an outfit that relocated farmers with free soil leanings, paying their passage to Kansas from states such as Connecticut and Maine. Abbott was now an officer with a militia, bent on making sure that if Kansas gained statehood it would be as a free state. Abbott was on a trip back East soliciting funds to purchase weapons for his militia.

During visits to Hartford, Conn., and Providence, R.I., Abbott had already raised enough money to buy 100 Sharps rifles, also known as Beecher’s Bibles. In New York, he connected with Olmsted and dubbed him acting commissioner of his free state activities. Olmsted raised more than $300 for Abbott’s cause from fellow Eastern abolitionists including Horace Greeley, editor of the New York Tribune and coiner of the term Bleeding Kansas.

Ever diligent, Olmsted decided to talk with an expert before purchasing weapons for Abbott’s militia. He consulted a veteran of European warfare, a man who had fought under Garibaldi during the turmoil that gripped Italy in 1848. In this expert’s opinion, Abbott’s militia already had enough Beecher’s Bibles and other assault weapons. What was needed was a defensive weapon to stave off attacks.

So Olmsted went to the New York State Arsenal and used the money he’d raised to purchase a mountain howitzer and ammunition. Olmsted recognized that he was involved in a dangerous activity. To keep Abbott apprised, Olmsted sent him a series of letters employing code (such as “H” for howitzer). Abbott referred to Olmsted as a “prompt and energetic friend of Kansas.”

Olmsted’s howitzer was mounted in front of the Free State Hotel, on the future site of the Eldridge Hotel. When Lawrence was sacked on May 21, 1856, (an attack that preceded Quantrill’s raid) the weapon was seized by a marauding band of South Carolinians. But the free-state militia got the cannon back as part of a prisoner exchange. It saw “prominent service” — in the words of one scholar — during the ensuing Civil War, and was ultimately retired to the collection of the Kansas State Historical Society.

That’s quite a tale for a howitzer. And it’s yet another fascinating episode in the life of Frederick Law Olmsted, landscape architect, journalist, abolitionist and friend of Kansas.

Justin Martin, who was raised in Lawrence and Overland Park, is author of “Genius of Place: The Life of Frederick Law Olmsted” (Da Capo). He lives in Forest Hills Gardens, N.Y. His father, Rex Martin, is an emeritus philosophy professor at Kansas University.